1. Field of the Invention
The present invention relates to a feeding device for a smart antenna, and more particularly to a feeding device that outputs a plurality of different signals via switching of the switching circuit.
2. Description of the Prior Art
With the evolution of wireless communication technologies, quantity of antennas equipped within an electronic product increases. For example, standard of wireless local area network (WLAN) IEEE 802.11n supports multi-input multi-output (MIMO) communication technique; and thus a related electronic product may receive and transmit radio signals synchronously via multiple sets of antennas, to increase data throughput and transmission distance in a system without increasing bandwidth or transmit power expenditure. Such that spectrum efficiency and data rate of the system can be effectively enhanced, and communication quality can be improved as well.
In the prior art, each antenna of a MIMO system has a fixed polarization direction, and is unable to be adjusted based on system requirements. Under this condition, transmitters and receivers may have polarization loss due to antenna polarization mismatch, which results in poor transmission efficiency. Hence, if polarization directions of each antenna can be adaptively adjusted according to circumstances of the transmission environment, the polarization loss of each antenna would be minimized, and thereby the transmission efficiency can be maximized.
However, to achieve the goal that adequately adjusts the polarization direction of the antennas is bound to increase difficulties in designing an antenna feeding network. In the prior arts, multiple sets of feeding networks are used to have feeding signals outputted individually for supplying antennas of various polarization directions. In this way, the layout complexity of printed circuit boards and the size of electronic products are both increased.